Shaft seal



931. F. D. PELTIER ET AL f 1,325,913

SHAFT SEAL Filed Feb. 8, 1927 Patented Oct. 6,, 1931 UNI ED STATESPATENT orrlcs rnmx'nmnorn'ns mum in EIMEB wrnnnnone, or mam,

ASSIGNOBS, BY MESNE ASSIGNMENTS, TO SEBVEL, INQ, OF m YORK, N. Y, A.GOR- rona'rron or DELAWARE SHAFT SEAL Application filed February 8,1927. Serial No. 180.38..

Our invention relates to shaft seals and is particularly adapted to thattype of refrigerating system wherein is' employed a compressor having ashaft projecting from within the compressor housing to the outside. In

this type of compressor difiiculty has been en? countered in obtaining agas tight seal for this shaft to prevent leakage around this shaft whereit passes through the compressor housing. When such a compressor is usedin con nection with a refrigerating system, it is particularly importantthat no such leakage occurs -as not only might the presence of therefrigerant inv the atmosphere be obj ectionable but its loss from therefrigeration system would impair and finally prevent the operation ofthe system. Our invention hereinafter described accomplishes this andother desired rezlults by means of a simple and eifeetive gas se c Fig.1 is a cross-sectional drawing showingthe'gas seal assembly; Fig. 2shows a crosssectionalview ofportions of the seal ;and Fig. 3 is an areadiagram of the seal. Y

Referring to Fig. 1, reference characterlO designatesa crank shaft whichprojects from the interior of the crank case of the compressor to theexterior and at this'end is supported by and rotates in bearing 11.Bearing 11 is in turn supported in "bearing plate 12 which is secured tothe crankcase by bolts 9 and a washer (not shown) so as to form a gastight joint between these two members, namely, the crank case and thebearing plate 12. Bearing plate 12 is provided with an annular hardenedsteel ring 13 having a smooth 14 is of such a diameter as to make a snugfit within the spool 14 and thus center the spool 14 on the shaft 10 atall times. Hermetically sealed to 'the'spool 14 at its outer en largedend is the circumferentially corruas a bellows. The opposite end ofbellows 17 is hermetically sealed to the annular ring 19 of suitablemetal andmade with a smoothflat inwardl projecting face in contact withthe outwar ly projecting face 24 of annular ring 13. A spiral spring 21surrounds spool 14 and exerts a force which tends to force bearing ring19 against bearing ring 13. The spool 14 is firmly fixed to the crankshaft 10 by the nut 15 and gasket 16 and causes the bellows 17 to rotatewith the shaft 10 which bellows communicates this motion to the annularbearin 'ring19 which, owing to its flexible mounting, is free to conformwith the surface of the stationary'annular bearing ring 13 andhenceforms a gas tight seal therewith. Gas which leaks out between the shaft10 and the bearing 11 passes between the spool 14 and the annularbearing ring 19 and is entrapped within the bellows 17. The gas inbellows 17 is under approximately the same pressure as the gas in thecrank case of the compressor. A

cover plate 23 is provided and secured in place by bolts 9. Its purposeis to prevent the collection of an undue amount of dirt around the shaftseal and to give a more sightly appearance to the assembly. The thrustexerted by the spring 21 and the gas under pressure in the crank caseand the bellows 17 which tends to force the shaft to the left, as shownin Fig. 1, is taken by the hardened'steel thrust washer 22 which is freeto turn on the crank shaft 10 and on the hub of the bearing late 12. Thepressure of the gas in bellows 1 acts in conjunction with spring 21 toforce bearing ring 19 against bearing ring 13 and to thus form a gastight seal between the two.

Since the other two points of possible leakage in this assembly areclosed by the gasket 16 and the gasket; (not shown) between the bearingplate 12 and the crank case, this last gas tight seal forms the finalseal in the assembly.

It has been stated in the above that the gas pressure within the bellowswould act to force the sealing surfaces together. This is shown by meansof Figs. 2 and 3, as follows:

Fi 2 is a cross section of the bellows assemb y and Fig. 3 is an endprojection of areas of pressure in the seal showing only the circlesboundin the areas referred to in the following description.

Letter (1 represents the exterior diameter of the bellows, the crosssectional area of which is represented by A and which is bounded bycircle 1.

d, represents the interior diameter of the bellows, the cross sectionalarea of which is represented by A and which is bounded by circle 4,

d, represents 'thediameter of a hypothetical circle whose area A isequal to the mean' of the areas A1 and A, (A, 4A1 X A4) of the bellowsto have a value of X pounds per unit area. If both ends of the bellow-swere closed the force exerted to expand the bellows longitudinally wouldbe equal to the unit force acting on an area which is equivalent to themean area of the internal and external areas of the corrugations, or inother words, the hypothetical area A However,

the right hand end is but partially closed by the bearing ring 19. Theeffective opening left in this end has a diameterequal to the meandiameter'd of the sealing surfaces.-

Of course, this opening does not open to the atmosphere but to the crankcase of the compressor so that the absolute pressure Within the openingis X pounds per unit area.

Now, consider the forces exclusive of the force exerted by spring 21.acting on the bearing ring 19. That annular portion of it within themean circumference of 'the bearing surface 24 will be acted u on on bothsides bv the pressure X and hence will have no tendency because of thesepressures to move longitudinallv either wav. However, that annularportion of bearing ring 19 included between the circumference of thehvpothetical circle 2 and the mean ircumference of the bearing surfacesis subiected on its side adjoining the bellows to the pressure X and onits opposite side to atmospheric pressure. Hence. the total resultantforce tending to move the bearing ring to the right will be equal tothis annular area included between the hypothetical circle 2 and themean circumference of the bearing surface 24 represented by' circle 3multiplied by the diflerenoe between the pressure X and at- -facesincontact mospheric pressure. This difierence in pressures is what iscommonly termed gauge pressure.

In the above discussion it has been assumed that the mean diameter ofthe bearin surfaces is l'essthan the diameter of the othetic'al circle2. If, on the other hand, the

mean diameter of the bearing surface is greater than the diameter of theh pothetical circle 2, that annular portion 0 the ring 19 includedbetween the mean circumference of the bearing surface and thehypothetical circle 2 will be subjected on the side away from thebellows to the pressure X and on the side toward the bellows toatmospheric pressure and hence will tend to move to the left and openthe seal. Therefore, the

. circle, the desired force to hold the sealing surfaces together ma be'obtained. Of course, this force will directly dependent on the pressureexisting in the bellows and this is to be desired as the increase intendency of leakage past the sealing surfaces due to an increase inpressure will be offset b an increase in force acting to force the seaing surfaces together. It is undesirable that a force sufiicient toprevent leakage at the highest pressure possible in the crank case andbellows, should be exerted at times when lower pressures exist, for atsuch times this excessive force would cause unnecessary friction andwear. The spring 21 is provided to aid the above force to keep thesealing surand is necessary when atmospheric pressure is greater thanthe pressure in the bellows as is the case, if methyl chloride is used,only when drawing a vacuum on the system preparatory to introducing thecharge of methyl chloride,

Having described our invention, what-we claim is:

1. A shaft seal comprising a spool adapted to fit snugly to the shaft torotate therewith and having an enlarged end, a bellows her-- meticallysealed to. said end and having a given mean effective diameter, abearing ring surrounding said spool and hermetically sealed to saidbellows, a bearing surface adj acent the bearing surface of said ring,said mean effective diameter being of greater dimension than the meaneffective diameter of the bearing surface of the bearing rin and acompression spring between saidv on and bearing ring.

2. A shaft seal comprising aspooladapted to fit snugly to the shaft torotate therewith and having an enlarged end, a bellows herneaaersmetically sealed to said end and having a given mean effective diameter,a bearing ring surrounding said spool and hermetically sealed to theother end of said bellows and a bearing surface adjacent the bearingsurface of said ring, said mean efiective diameter being of greaterdimension than the mean effective diameter of the bearingsurface of thebearing ring.

8. In a compressor or the like, a shaft having a shoulder and a bearingportion within the shoulder, a spool surrounding the bearing portion andarranged to rotate with the shaft, said spool having an enlarged end, abellows hermetically sealed to said end and having a given meaneffective diameter, a bearing ring surrounding said spool andhermetically sealed to said bellows, a bearing surface adjacent thebearing surface of said ring, said mean efiective diameter being ofgreater dimension than the mean effective diameter of the bearingsurface of the bearing ring and a nut on said shaft for pressing saidspool against said shoulder.

4. In a compressor or the like, a shaft having a shoulder and a bearingportion within the shoulder, a. spool surrounding the bearing portionand arranged to rotate with the shaft,

said spool having an enlarged end, a bellows hermetically sealed to saidend and having a given meaneffective diameter, a bearing ringsurrounding said spool and hermetically sealed to said bellows, abearing surface adj acent the bearing surface of said ring, said meaneffective diameter being of greater dimension than the mean effectivediameter of the bearing surface of the bearing ring, a nut on said shaftfor pressing said spool against said shoulder and a compression springbetween said end and bearing ring.

5. In a compressor or the like, a crank shaft, a shoulder on said crankshaft between portions of different diameters, a spool mounted on theportion of smaller diameter and abutting against said shoulder, athreaded portion of said crank shaft adjacent said portion of smallerdiameter, a nut having internal screw threads engaging said threadedportion and holding said spool against said shoulder, an enlarged end onsaid spool, a bellows hermetically attached to said enlarged end, abearing ring hermetically attached to the other end of said bellows anda bearing surface adjacent the bearing surface of said ring, theremainder of said crank shaft from said threaded portion outward beingof less diameter than said threaded portion.

6. In a compressor or the like, a crank shaft, a shoulder on said crankshaft between portions of different diameters, a spool mounted on theportion of smaller diameter and abutting against said shoulder, athreaded portion of said crank shaft adjacent said portion of smallerdiameter, a nut having internal screw threads engaging said threadedportion and holding said spool against said shoulder, an enlarged end onsaid spool, a bellows hermetically attached to said enlarged end, abearing ring hermetically attached to the other end of said bellows, acompression spring between said enlarged end and said bearing ring andsupported by said spool and a bearing surface adjacent the bearingsurface of said ring, the remainder of the crank shaft from saidthreaded portion outward being of less diameter than said threadedportion.

7. In a compressor or the like, a crank shaft, a shoulder on said crankshaft between portions of different diameters, a spool mounted on theportion of smaller diameter and abutting against said shoulder, athreaded portion of said crank shaft adjacent said portion of smallerdiameter, a nut having internal screw threads engaging said threadedportion and holding said spool against said shoulder, an enlarged end onsaid spool, a bellows hermetically attached to said enlarged end, abearing ring hermetically attached to the other end of said bellows, acompression spring between said enlarged end and said bearing ring andsupported by said spool and a bearing surface adjacent the bearingsurface of said ring, the effective area of said bellows being greaterthan that of said bearing surfaces whereby pressure within the bellowsforces said bearing surfaces together and the remainder of said crankshaft from said threaded portion outward being of less diameter thansaid threaded portion.

In testimony whereof we hereunto affix our signatures.

FRANK DESNOYERS PELTIER,

ELMER WIDERBORG.

